Impulse coupling



Dec. 16, 1924.

' R. M. CRITCHFIELD IMPULSE COUPLING Eilegi July 24, 1923 2 SheetsSheet 1 7 g; /Tw/ Q@ a w .ZYUEHZE Dec, 16,

R. M. CRITCHFIELD IMPULSE COUPLING Ffilegl July 2.4, 1925 2 Sheets-Sheet 2 Patented Dec. 16, 1924.

(OFFICE.

ROBERT M. CRITCHFIELD, OF ANDERSON, INDIANA, ASSIGNOB. TC GENERAL IVIOTORS CORPORATION, OF ANDERSON, INDIANA, A CORPORATION OF DELAWARE.

IMPULSE COUPLING.

Application filed July 24, 1823. Serial No. 853,596.

To all whom it may concern:

Be it known that I, ROBERT M. GRITOH- FIELD, a citizen of the United States of America, residing at Anderson, county of Madison, State of Indiana, have invented certain new and useful Improvements in Impulse Couplings, of which the following is a full, clear, and exact description.

This invention relates to impulse couplings, particularly adapted for use in con nection with magnetos arranged for furnishing ignition to an internal combustion engine, and relates more particularly to that type of mechanism adapted to produce the maximum current flow or spark during the engine starting operation by a quick acceleration of the magneto armature shaft.

One of the objects of this invention is to produce intermittently rapid acceleration of the magneto shaft while cranking the engine, and then to drive the shaft continuously at relatively higher speeds and without changing the timing of the magneto relative to engine operation.

Another object of the invention is to pro vide means for relieving the magneto from the injurious effects caused by suddenly retarding rotation of the magneto shaft.

Other and further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of embodiment of the invention is clearly disclosed.

In the drawings:

Fig. 1 is a top plan view of the driving member or shell included in the present invention.

Fig. 2 is a vertical mid-sectional view of the impulse coupling.

Fig. 3 is an end view of the driven member, looking in the direction of the arrow 3 in Fig. 4.

Fig. 4 is a side view of the driven member.

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 2, the parts thereof being shown in normal position.

Fig. 6 is a sectional view taken on the line 66 of Fig. 2, showing the dog members in engagement with the latch plate.

Fig. 7 is a view similar to Fig. 5, showing the impulse spring in its fully compressed position, the auxiliary spring being out of contact with the driven member.

Fig. 8 is a view similar to Fig. 6, showing the dog members just about to be released from engagement with the latch plate.

In the drawings, a magneto armature shaft 20 which is journaled in a magneto frame 21., is provided with a tapered por tion and a reduced threaded portion 23. Fran'ie 21 is provided with a recessed por tion 24. A latch plate 25, provided with a central aperture and with a notch 26 cut in the periphery thereof and included by surfaces 27 and 28, is attached to the frame 21 by screws 29. A driven member 35 is provided with a tapered recess 37 and a cylindrical recess 38 forming a continuous aperture through the member 35. Member 35 is provided with cylindrical bearings 39 and 40 on opposite sides thereof, and a lug 41 provided with a square notch 42. Dog members 45 and 46 provided with ears 51, are attached to the member 35 by rivets 47 and 48 which are received by holes 49 and 50, respectively, in member 35. An apertured yoke member 52, provided with diametrically oppositely extending arms 53 is loosely mounted on the bearing 39.

A driving member comprises a cupshaped shell 61 provided with notches 62 in the rim thereof in which the ends of arms 53 are received. The shell 61 is provided with a rectangular opening 63 adapted to receive the hooked end 64 of a leaf spring This spring 65, together with a backing plate 66, are secured to the shell 61 by rivets 67 and 68. Shell 61 is provided with a central opening 69 adapted to receive the bearing 40 which serves to support the shell 61. Located in the annular recess 70 formed by the shell 61 and the driven member 35 is a coiled spring 71,- one end thereof abutting against the right hand surface of the lug 41, as viewed in Fig. 5. The opposite end of spring 71 is provided with a button 72 which abuts against a block 73 secured to the shell 61, as shown in Figs. 5 and 7. Normally the block 73 is held against a cushioning pad 74, of leather or the like, by the pressure of spring 71.

This assembly of the driven and driving members is adapted to be attached to the magneto armature shaft 20, the tapered recess 37 of member 35 receiving the tapered portion 22 of the shaft 20, and the reduced threaded portion 23 of shaft20- extending through the. recess 38 in member 35. key 35 which engages a key way out in the between the vmember 35 and the shaft 20. A nut 75, provided with a flanged head 76 slightly larger than the aperture 69 in shell 61 is adapted to engage the threaded portion 23. When nut 75 is screwed toward the shaft 20 until the flanged head 76 engages the driven member 35, the driving member 60 is held in position with respect to the driven member 35, and the driven -member is retained on the shaft 20.

Attached to the base of the shell 61 is an annular member 80 provided with diametrically opposite ears 81 forming one member of an Oldham coupling. The other members of this Oldham coupling comprise a flange member 82 which. is attached to a drive shaft 83 by a pin 84. This member 82 is provided with ears 85, and is so located on the shaft 83 that the cars 81 and 85 are disposed at 90 degree angles with respect to each other. A disc 87 provided with four equidistant notches 86 cut in the" periphery thereof, is positioned between. members 80 and 82. The ears 81 and are adapted to engage in these notches and thus a driving connection between the drive shaft 83 and the driving member 60 is effected.

Mode of operation: The apparatus disclosed is arranged for counterclockwise rotation as viewed in Figs. 5 and 7, or clockwise as viewed in Figs. 6 and 8. When operated at cranking speed of the engine, one of the dogs, such as dog 45, will be received by the notch 26 of the latch plate 25, tlie ear 51 of the dog engaging the surface 28, thus arresting movement of the driven member 35. As the driving member 60 1'0- tates, the hooked end 64 of spring 65 will be cammed out of the notch 42 and will ride on the periphery of the driven member 35. At the same time, the yoke member 52, which is rotating in a clockwise direction, as viewed in Fig. 6 is having its camming surface 52 moved upwardly toward the ear 51 of dog member 45. Thus the member 52 moves the car 51 out of the notch 26. During this rotation of the driving member 60, the spring 71 is compressed beyond its initial state, and Fig. 7 shows the spring in its fully compressed state. Fig. 8 shows the dog 45 just about out of engagement with. surface 28 of plate 25. When the dog 45 is released from the surface 28, the spring 71 is released and quickly rotates the driven member 35 in a counter clockwise direction, as viewed inFigs. 5 and 7, to produce the rapid acceleration of the armature shaft required for sparking. l/Vhen the driven member overtakes the driving member, the cushioning pad 74 will strike the block and be compressed. Therefore the pad 74 tends to absorb the energy of impact of the driving member striking the driven. member. (hen the driven menr ber overtakes the driving member, the hooked end 64 of the leaf spring 65 will drop into the notch 42, and during compression of the pad 74, the end 64 will be cammed partially out from the notch 42. As the pad 74 returns to normal shape, the hooked end 64 will return to normalposition in the notch 42. By virtue of this motion of the leaf spring which produces bending thereof, said spring assists in absorbing the energy of impact between the driving and driven members.

As the driving member GO- continues to rotate, the dog 46 will engage the notch 26 and again the rotation of the driven member 35' will be momentarily arrested untilthe spring 11 again reaches fully compressed position. The dog 46 will then be released from the notch inv the manner described, and the driven member 35 will again be quickly rotated to produce rapid acceleration of the magneto shaft for sparking purposes. Thus, for each complete revolution of the driving member 60,'t-here will be two operations of the impulser, and two sparking impulses generated by the magneto.

At engine speeds substantially higher than cranking speed, the free ends of the dogs 45 and 46 will be thrown outwardly by centrifugal force against the inner surface of the shell 61, and the position of springs 65 and 71, and the relative position of the driving member 60 and the driven member 35 will be such as shown in Fig. '5. Springs 65 and'71 both serve as connecting springs between the drivi-n member 60, and the driven member 35, and spring 65 tends to maintain the members 60 and 35 in the same relative position as these higher speeds so that the ignition timingwill not be varied during engine operation but will be maintained substantially constant.

In a construction wherein the impulse spring provides the only drivingconneetion between the driving and driven members, the impulse spring must be stiffer than necessary for providing impulses, because the variation in relation between these members must be limited when the coupling is operated at higher speeds; The, use of the leaf spring 65 permits the use of an impulse spring which is less stifl than in the con struction referred to, since the impulse spring is relievedof the duty of maintaining a constant driving connection between the driving and driven members. Therefore the impact which occurs when the driven member overtakesand strikes the driving member is materially reduced.

While the form of mechanism herein shown and described constitutes a preferred form of embodiment of the invention, it to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What I claim is as follows:

1. An impulse coupling for magnetos comprising the combination with rotatable driving and driven members; of an impulse spring through which the driving member tends to drive the driven member; and means for intermittently stopping the driven member to store energy in said spring, and for releasing said driven member whereby acceleration of the driven member is produced by said spring and the driven member overtakes the driving member; provision for rendering said means inoperative; and a device for yieldingly connecting said members to maintain a substantially constant relation between said members when said means are inoperative, said device including a leaf spring connected with one of said members and yieldingly urged into a recess provided by the other member.

2. An impulse coupling for magnetos comprising the combination with rotatable driving and driven members; of a driven member including a notched portion, and a driving member; of a leaf spring attached to said driving member and having a hook portion normally received by said notch to maintain a substantially constant relation between said members; an impulse spring through which the driving member tends to drive the driven member; and means for intermittently stopping the driven member to store energy in said spring, and for releasing said driven member whereby acceleration of he driven member is produced by said spring and the driven member overtakes the driving member, said means being rendered centrifugally inoperative at higher speeds; the yielding of said leaf sprin permitting operation of said means an tending to cushion the impact of the driven member against the driving member.

8. An impulse coupling for magnetos comprising the combination with rotatable driving and driven members; of an impulse spring through which the driving member tends to drive the driven member, said driving member including a shell portion enclosing the driven member; means for intermittently stopping the driven member to store energy in said spring, and for releasing said driven member whereby acceleration of the driven member is produced by said spring and the driven member overtakes the driving member; provisions for rendering said means inoperative; and a leaf spring attached to the exterior of said shell and having a hook portion extending within the shell and received by a recess provided by the driven member whereby said mem bers may be yieldingly connected.

In testimony whereof I hereto aiiix my signature.

ROBERT M. CRITGHFIELD. 

